"Longer explanation: This feature has always triggered in one of two ways: keyword tab key search term and keyword spacebar search term. We have disabled the latter because we believe that it was resulting in unintentional triggering for some users."

The second triggering did happen to me occasionally so I understand the rationale behind this change but switching to tab is going to seriously require some re-learning of muscle memory. Since custom search engines seems like a pro feature and pros probably are used to them by now, maybe let it be?